Pabbay (Scottish Gaelic: Pabaigh,pronounced [ˈpʰapaj]) is one of the Barra Isles at the southern tip of the Outer Hebrides of Scotland. The name comes from Papey, which is Norse for "island of the papar" (i.e. monks). At only 250 hectares (0.97 sq mi), it never had a large population, and, after all the able-bodied men were killed in a fierce storm while out on a fishing trip on 1 May 1897, it was abandoned in the early twentieth century.

The National Trust for Scotland has owned the island since 2000. With only two sheep left on the island (at July 2007) and few if any other permanent mammalian residents, Pabbay is consequently home in summer to many ground-nesting birds due to the absence of predators.

The island was the site of a Celtichermitage, and a Pictish carved stone dates from that period. Remains of an Iron Age settlement can also been seen on Pabbay.

The name of Pabbay is used for one of the three houses of Castlebay Secondary School. The other two are Mingulay and Sandray.